I have a stock 350/300 hp in my '69 Pace Car with the Turbo 350 and 3.08:1 gears. I am rebuilding a good date coded quadrajet for it but have come across several different jets in the donor carbs, anywhere from 64's to 67's.

Anybody ahve any comments or suggestions on what jets I should try initially when I put the rebuilt carb on? I really want it to run a little on the lean side, so I am leaning towards the 64's.

Bruce

JET:74 / ROD:42K / SEC:AU
As recommended by Sean Murphy Inductions for my 300hp 327

The 60 series jets are quite hard to find and may be valuable to guys who do area equivalent jetting in their race carbs. Most of the jets you find are 70 and larger.
Lars Grimsrud has an excellent paper on Q-jet tuning:

http://www.corvetteclub.org.uk/files/downloads/how_to_tune_a_qjet.pdf

Q-jets very too much for any set number to be correct for any engine. The 69 carbs are designed to use 66-67 jets with a small block if you have the correct carb.

JET:74 / ROD:42K / SEC:AU
As recommended by Sean Murphy Inductions for my 300hp 327


Jet sizes are HIGHLY dependent on main air bleed size. Unless you are duplicating main air bleeds, blanket jet recommendations don't work.

PaceCar... The two 7029202 carbs I have dis-assembled have had 67 jets installed. Use the 67 jets and fine tune with metering rods to get a lean cruise mixture. I *think* the OEM 7029202 rods were 39b.

Also... going by memory here... the 7029202 carb has a primary pull-over enrichment system. If this is true, that explains the smaller-than-normal jetting, as the POE adds additional primary fuel. In this case, 74 main jets will be WAY too rich.

I highly suggest grabbing a copy of the Doug Roe Q-jet book, and also the new Cliff Ruggles book. Mandatory reading before messing with Q-jets.

Some Quadrajet carburetors have a fuel pull-over enrichment system to provide added enrichment and improved fuel control during higher engine speeds and carburetor air flows (Figure 11).

Two calibrated holes, one in each primary bore, are located either just above or just below the choke valve and feed fuel from tubes that extend into the float bowl. During high carburetor air flows, low pressure created in the air horn bore pulls fuel from the high-speed fuel feeds, supplementing fuel flow from the primary main metering system. The pull-over enrichment system begins to feed fuel at approximately 8 lbs. of air per minute and continues to feed at higher engine speeds to provide extra fuel necessary for good engine performance.

On those carburetor models that have the two calibrated holes located just below the choke valve (See Choke System 4MV), the pull-over enrichment system feeds additional fuel at closed choke for good cold engine starting. Calibrated air bleeds, located in the air horn, are used with this system.

The pull-over enrichment system allows the use of slightly leaner mixtures during part throttle operation and still provide enough fuel during high-speed operation. This feature gives added refinement to the fuel mixtures for exhaust emission control.

http://www.tocmp.com/manuals/Carbs/Rochester/QJet/HTML/MCarbRoch1973_4M_0009.htm

Yup... that is the system I was talking about. Supplemental flow from the POE means you don't need as much from the main jet.

If I am right, and the 7029202 has Primary POE, you'll see an extra set of brass tubes hanging from the airhorn into the fuel bowl to feed the holes described in the text above.